Heterogeneity of human B lymphocytes as revealed by monoclonal antibodies

Two monoclonal antibodies directed at determinants on human B lymphocytes were produced and characterized by indirect immunofluorescence. The antibodies, BL13 and BL14, were found to be specific for B cells, since they did not react on red cells, platelets, granulocytes, monocytes or T lymphocytes. BL14-associated antigen was present on most of the circulating and tissular B cells, whereas that detected by BL13 was mainly restricted to a subpopulation preferentially homed in germinal centers of secondary follicles of lymph nodes and tonsils, which did not circulate under normal conditions and disappeared once B cells were activated by mitogens. Immunoprecipitation studies demonstrated that BL13 precipitated an antigen of approximately 160,000 d. Pathological studies confirmed the specificity of BL13 and BL14 antibodies for B lymphocytes, since they never reacted with non-B malignancies. BL14 bound to nearly all malignant B-cell proliferations except very immature and plasmacytoma cells. In contrast, BL13 was always found to be negative on acute lymphocytic leukaemias, prolymphocytic leukaemias, hairy cell leukaemias and plasma cells, whereas it detected 40-50% of chronic lymphocytic leukaemias and Burkitt or non-Burkitt lymphomas. These results led us to hypothesize several compartments for B-lymphocyte differentiation, either in central (bone marrow) or peripheral lymphoid organs, with BL13 antibody defining one compartment in the germinal centers.